PROJECT SUMMARY/ABSTRACT Nearly 20% of women in the United States experience clinically significant depressive symptoms during pregnancy or the postpartum period. Pregnant and postpartum women would benefit from easily accessible, non-pharmacologic, and inexpensive self-management approaches, such as via the internet, to prevent development of symptoms and/or intervene with current symptoms. At present, no systematic internet-based self-management approaches designed to prevent or treat perinatal depressive symptoms exist in the U.S. Our proposed study will address this gap by evaluating an internet-based self-management program to prevent and intervene with perinatal depressive symptoms? ?Mamma Mia?? in a large scale randomized controlled study. ?Mamma Mia? is a self-guided program that women will begin during the ?teachable moment? of pregnancy, when intrinsic motivation for self-management is high, and will complete by six months postpartum. The program contains a novel combination of components designed to enable women to enhance self-efficacy, emotional self-regulation, and perceived social support. With our Norwegian colleagues, we recently established the feasibility and efficacy of ?Mamma Mia? for perinatal depressive symptoms in 1342 women in Norway and we piloted a demonstration version in the U.S. The proposed study builds upon our findings by adapting the intervention for a diverse U.S. audience; by using national and hub-based (local) strategies for recruiting women of diverse racial/ethnic and socioeconomic status; and, by adding a small amount of guided support (?Mamma Mia Plus?). The overall goal of this three-arm longitudinal randomized controlled trial is to evaluate the effects and mechanisms of this internet-based self-management approach in diverse women in the U.S. (n=1950). Enrolled pregnant women will be randomly assigned to one of three groups: (1) ?Mamma Mia? in which they engage in 44 modules throughout their pregnancy and the first six months postpartum; (2) ?Mamma Mia Plus? in which they engage in the ?Mamma Mia? modules plus receive brief guided support from a registered nurse; or (3) usual prenatal/postpartum care. The first specific aim is to evaluate effects by group on the primary outcome of interest, depressive symptom severity, over time. The second aim is to evaluate effects by group on subjective well-being, anxiety, and stress. Using a conceptual framework based upon Individual and Family Self-Management Theory, the tertiary aim is to evaluate possible mediators (self-efficacy, emotion self-regulation, perceived support) and possible moderators (e.g., race/ethnicity, type of healthcare clinician) of this self-management approach, which may differ from those in the Norwegian RCT. We seek to shift the clinical paradigm regarding prevention of perinatal depressive symptoms by using an internet-based self-management approach that allows for wide-ranging accessibility and large reach to individuals across all geographical regions of the U.S. If proven efficacious, ?Mamma Mia? may be a low-cost, sustainable, and translatable option for prevention of and intervention in perinatal depressive symptoms.